Eh ada je! A few of my mum friends experienced this actually, ada yang UPT negative sampai 3-4 kali tapi tengok-tengok memang pregnant, hCG hormone dia lambat naik je dulu so the test couldn't detect it yet. Timing of the test matters a lot, kena test pas morning urine paling pekat, and some people's hormones rise slower than others, especially if implantation late sikit. Best thing is jaga diri mula-mula, monitor signs macam morning sickness, breast tenderness ke, then pergi clinic untuk blood test je, that's way more reliable than UPT sebab dapat detect hormone levels yang lebih kecil. Good luck!